1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus, and more specifically to an information recording/reproducing apparatus having a plurality of operation modes of different power consumption, and having a battery as a power supply.
2. Description of the Related Art
Japanese Patent Application Publication No. 9-81524 discloses mobile electronic equipment designed to reduce the power consumption of the mobile electronic equipment such that a voltage of a battery can be boosted through a booster circuit only when the voltage of the battery becomes lower than the minimum voltage required to guarantee the operation of the equipment. That is, the power consumption in the booster circuit can be reduced by operating the booster circuit only when the voltage of the battery drops.
Japanese Patent Application Publication No. 8-149178 discloses an electric current control method of reducing the power consumption in the entire apparatus by restricting the passage of the electric current from the power supply corresponding to functional blocks except necessary functional blocks depending on the use state of the apparatus.
Recently, a digital camera has been developed to have an audio recording function of recording audio in semiconductor memory, and an audio reproducing function of reproducing music data generated as a file which can be recorded in the semiconductor memory represented by MP3 equipment.
This type of digital camera indicates different power consumption between an image recording/reproducing mode in which it functions as an original digital camera, and an audio recording/reproducing mode in which the above-mentioned audio recording and reproducing functions are used.
That is, the above-mentioned digital camera is loaded with an image processing large scale integrated circuit (LSI) for recording/reproducing an image and an audio processing LSI for recording/reproducing audio. The image processing LSI consumes a large amount of power because it operates at a high speed. On the other hand, the audio processing LSI requires a process performed at lower speed than the image processing LSI, thereby operating with low power consumption. Normally, a low-speed LSI can be operated at a lower voltage than a high-speed LSI.
It is desired that power is supplied from different power sources to the above-mentioned image processing LSI and audio processing LSI. However, the same power source actually supplies power to the both image processing LSI and audio processing LSI because of the size restriction of equipment, and the power supply voltage adapted to the high-speed image processing LSI is also supplied to the low-speed audio processing LSI. Therefore, although a digital camera is used in the audio recording/reproducing mode (that is, although the image processing LSI is not used), a voltage higher than a necessary voltage for the operation of the audio processing LSI is supplied to the audio processing LSI. As a result, the entire power consumption unnecessarily increases.
Furthermore, with respect to a digital camera, it is necessary to operate the image processing LSI, an electric flash device, a lens drive unit, a liquid crystal monitor, etc. in the shooting mode. Therefore, since the digital camera's circuit is designed with large power consumption and the fluctuation in power consumption by the charge of the electric flash device, the drive of the lens, etc. taken into account, the operation-terminating voltage of the battery to be checked is set high. Accordingly, although the digital camera is used in the operation mode in which the power consumption is low and it is not likely to incur large fluctuation in power consumption (that is, in the audio recording/reproducing mode), the above-mentioned battery check disables the operation in the state of a high voltage of the battery. Since the audio recording/reproducing functions are intended to record the proceedings of a meeting, play back music in the field, etc., a long-time operation is required. However, since the set operation-terminating voltage of the battery is high, the system is disabled before fully exhausting the battery.